diff --git a/sw/ground_segment/tmtc/stereo_demod.ml b/sw/ground_segment/tmtc/stereo_demod.ml
new file mode 100644
index 0000000000..be2d05deb5
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+++ b/sw/ground_segment/tmtc/stereo_demod.ml
@@ -0,0 +1,139 @@
+(*
+ * $Id$
+ *
+ * Hardware modem receiver
+ *  
+ * Copyright (C) 2004 CENA/ENAC, Pascal Brisset, Antoine Drouin
+ *
+ * This file is part of paparazzi.
+ *
+ * paparazzi is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * paparazzi is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with paparazzi; see the file COPYING.  If not, write to
+ * the Free Software Foundation, 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA. 
+ *
+ *)
+
+open Printf
+
+
+let modem_msg_period = 1000 (** ms *)
+
+module Tele_Class = struct let name = "telemetry_ap" end
+module Tele_Pprz = Pprz.Protocol(Tele_Class)
+module PprzTransport = Serial.Transport(Tele_Pprz)
+
+(** Monitoring of the message reception *)
+type status = {
+    mutable ac_id : string;
+    mutable rx_byte : int;
+    mutable rx_msg : int;
+    mutable rx_err : int
+  }
+(** Ivy messages are initially tagged "modem" and with the A/C
+id as soon as it is identified (IDENT message) *)
+let make_status = fun id ->
+  { ac_id = id; rx_byte = 0; rx_msg = 0; rx_err = 0 }
+
+let status_left = make_status "modem_left"
+let status_right = make_status "modem_right"
+
+
+(** Callback for each decoded message *)
+let use_pprz_message = fun status (msg_id, values) ->
+  status.rx_msg <- status.rx_msg + 1; (** Monitoring update *)
+  let msg = Tele_Pprz.message_of_id msg_id in
+  if msg.Pprz.name = "IDENT" then
+    status.ac_id <- Pprz.string_assoc "id" values;
+  prerr_endline (status.ac_id^":"^msg.Pprz.name);
+  Tele_Pprz.message_send status.ac_id msg.Pprz.name values
+
+(** Listen on a dsp device *)
+let listen_pprz_modem = fun pprz_message_cb devdsp ->
+  let fd = Demod.init devdsp in
+
+  (** Callback for a checksumed pprz message *)
+  let use_pprz_buf = fun status buf ->
+    status.rx_byte <- status.rx_byte + String.length buf;
+    Debug.call 'P' (fun f -> fprintf f "use_pprz: %s\n" (Debug.xprint buf));
+    pprz_message_cb status (Tele_Pprz.values_of_bin buf) in
+
+  (** Callback for available chars *)
+  let cb = fun status buffer data ->
+      (** Accumulate in a buffer *)
+      let b = !buffer ^ data in
+      Debug.call 'M' (fun f -> fprintf f "Pprz buffer: %s\n" (Debug.xprint b));
+      (** Parse as pprz message and ... *)
+      let x = PprzTransport.parse (use_pprz_buf status) b in
+      status.rx_err <- !PprzTransport.nb_err;
+      (** ... remove from the buffer the chars which have been used *)
+      buffer := String.sub b x (String.length b - x)
+  in
+  let buffer_left = ref "" and buffer_right = ref "" in
+  let cb_stereo = fun _ ->
+    let (data_left, data_right) = Demod.get_data () in
+    cb status_left buffer_left data_left;
+    cb status_right buffer_right data_right;
+    true in
+
+  (** Attach the callback to the channel *)
+  ignore (Glib.Io.add_watch [`IN] cb_stereo (Glib.Io.channel_of_descr fd))
+
+(** Modem monitoring messages *)
+let send_modem_msg = fun status ->
+  let rx_msg = ref 0 
+  and rx_byte = ref 0 
+  and start = Unix.gettimeofday () in
+  fun () ->
+    let dt = float modem_msg_period /. 1000. in
+    let t = int_of_float (Unix.gettimeofday () -. start) in
+    let byte_rate = float (status.rx_byte - !rx_byte) /. dt
+    and msg_rate = float (status.rx_msg - !rx_msg) /. dt in
+    rx_msg := status.rx_msg;
+    rx_byte := status.rx_byte;
+    let vs = ["run_time", Pprz.Int t;
+	      "rx_bytes_rate", Pprz.Float byte_rate; 
+	      "rx_msgs_rate", Pprz.Float msg_rate;
+	      "rx_err", Pprz.Int status.rx_err;
+	      "rx_bytes", Pprz.Int status.rx_byte;
+	      "rx_msgs", Pprz.Int status.rx_msg
+	    ] in
+    Tele_Pprz.message_send status.ac_id "DOWNLINK_STATUS" vs
+
+(* main loop *)
+let _ =
+  let ivy_bus = ref "127.255.255.255:2010" in
+  let port = ref "/dev/dsp" in
+  let options =
+    [ "-b", Arg.Set_string ivy_bus, (sprintf "Ivy bus (%s)" !ivy_bus);
+      "-d", Arg.Set_string port, (sprintf "Port (%s)" !port)] in
+  Arg.parse
+    options
+    (fun x -> fprintf stderr "Warning:ignoring %s\n" x)
+    "Usage: ";
+  
+  Ivy.init "Paparazzi stereo demod" "READY" (fun _ _ -> ());
+  Ivy.start !ivy_bus;
+
+  (** Listening on the given port (serial device or multimon fifo)*)
+  listen_pprz_modem use_pprz_message !port;
+
+  (** Sending periodically modem and downlink status messages *)
+  let send_left = send_modem_msg status_left
+  and send_right = send_modem_msg status_right in    
+  ignore (Glib.Timeout.add modem_msg_period (fun () -> send_left (); send_right (); true));
+  
+  let loop = Glib.Main.create true in
+  while Glib.Main.is_running loop do
+    ignore (Glib.Main.iteration true)
+  done